Rational design of a monomeric and photostable far-red fluorescent protein for fluorescence imaging in vivo Protein Sci. Yu D, Dong Z, Gustafson WC, Ruiz-González R, Signor L, Marzocca F, Borel F, Klassen MP, Makhijani K, Royant A, Jan YN, Weiss WA, Guo S, Shu X.